In formulating warewashing ("dishwashing") detergent compositions for use in automatic dishwashing machines, it is often desirable to include specialized ingredients referred to as wash additives. Certain wash additives are preferably introduced into the rinse cycle after an alkaline detergent wash has occurred. Therefore, as used hereinafter, "wash additive" refers to those materials which are intended for use, are most efficacious in a rinse portion of a wash session, and are intended to improve the appearance, sanitation or cleanliness of the ware washed in a machine ("automatic") dishwashing apparatus. Such wash additives include, but are not limited to, bleaches, soil anti-redeposition agents, enzymes and the classes of surfactants or surfactant blends known as rinse aids. Rinse aids are used to decrease spotting and filming on previously washed dishes, glasses and other household items, aiding drying and enhancing shine.
The required sequential addition of washing detergent and rinse aid can be achieved by manually introducing the rinse aid into the dishwashing machine after the washing detergent has been added and the dishes washed. This process is inconvenient, however, and requires a consumer to purchase and handle separate products.
Sequential addition of these ingredients can also be achieved by providing separate compartments in the dishwasher that will open at different times during the wash session. Currently available dishwashing machines have two compartments--one which opens at the beginning of the pre-wash cycle, and another which opens at the start of the wash cycle. Providing additional compartments requires a substantial retrofit of existing machine types or the design of new ones, which can be a costly undertaking in either case.
To overcome these problems, a number of detergent compositions have been disclosed which are intended to provide the delayed release of one or more of the ingredients in situ during the washing session. For example, Smith et al. (U.S. Pat. No. 4,972,017 ) discloses core particles comprising wash additives such as bleach or surfactants that are coated with a blend of crosslinked polyvinyl alcohol and alkyl cellulose. The coating is disclosed to remain intact in the alkaline environment of the wash cycle, but to rapidly dissolve in the lower pH of the rinse cycle. Kamel et al. (U.S. Pat. No. 5,230,822) disclose encapsulating particles of a core material, such as an enzyme, which may be incompatible with other detergent components, such as bleach. The coating of low-melting paraffin wax which is employed to coat the core material is selected to melt so that the active core material is released into the wash cycle. K. W. Chun et al. (U.S. Pat. No. 5,133,892) disclose a detergent tablet having at least two coating layers. The tablet is intended to provide sequenced release of a dishwashing detergent composition from the outer layer and a rinse aid from the inner layer. A polymer barrier layer separates the two layers.
While delayed release compositions have been used in the detergent and dishwashing arts, none of the prior compositions provide the convenience and performance necessary to be accepted by consumers. Therefore, a continuing need exists for a dishwashing detergent composition which comprises both a dishwashing detergent component and a rinse aid, wherein the rinse aid is released alter the detergent cleaning has been initiated or accomplished.